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Anatomy of the Middle Ear Structures
1. 3. Anterior wall / Carotid wall
A thin plate of bone separating Internal carotid
artery from the Middle ear cavity is the Anterior
wall.
In the anterior wall there is :-
1. Eustachian tube opening
2. Canal for Tensor tympani muscle
3. Canal for Chorda tympani nv.
4. Attachment for Anterior Malleolar ligament
2.
3. 4.Posterior wall / mastoid wall
There are five important sructures in the posterior
wall.
1. Aditus – opening of mastoid air cells into Attic
2. Pyramid – bony projection harbours the
Stapedius m. inserted to the neck of the Stapes
3. Facial nv. – vertical fallopian canal in the mastoid
containing facial nv.
4. Suprapyramidal recess
5. Infrapyramidal recess
4.
5. 5. Medial wall / labyrinthine wall
Medial wall is formed by the lateral wall of the labyrinth.
Important structures in the medial wall are-
1. Lateral semicircular canal
2. Horizontal tympanic fallopian canal for facial nv.
3. Oval window
4. Promontary
5. Round window
6. Processus cochleaformis- tendon of tensor tympani
m. takes a turn around this hook like projection and it
is the surgical landmark of the level of first genu of
facial nv.
6. 6. Lateral wall / membranous wall
Lateral wall consists of two parts –
a) Tympanic membrane :- medial side of tympanic
membrane forms the lateral wall of middle ear.
b) Scutum :- outer bony wall of the Attic is called the
scutum.
7. 7. Floor
Flooor is formed by a thin plate of bone
separating the middle ear cavity from the
Jugular bulb.
Congenital absence of bony plate leads to a
projection of jugular bulb inside the middle
ear cavity only covered by a layer of mucusa.
8.
9. 8. Roof
Roof is also formed by another thin plate of
bone called Tegmen tympani and it separates
the middle ear cavity from the middle cranial
fossa.
10.
11. Parts of middle ear
Middle ear cavity is classically divided into three
parts-
a) Epitympanum ( Attic )-above the level of pars
tensa
b) Mesotympanum – at the level of pars tensa
c) Hypotympanum – below the level of pars tensa
Another portion around the opening of
eustachian tube is termed as Protympanum.
12. Contents of middle ear
Middle ear contains –
a) Ossicles-
1. Maleus / Hammer bone
2.Incus / Anvil
3. Stapes / Stirrup
b) Muscles –
1. Tensor tympani
2. Stapedius
c) Nerves –
1. Tympanic plexus
2. Chorda tympani nv.
13. Ossicles of middle ear
A. Maleus / Hammer bone:- largest among the
three ossicles measuring 8 mm in length and
consists of head , neck , anterior process ,
lateral process and manubrium or handle
B. Incus / anvil :- it consists of body , short
process and long process
C. Stapes / stirrup :- smallest bone measuring
3.5 mm and consists of head, neck, two crura
and footplate.
14. Musscles of middle ear
Tensor tympani Bony tunnel
above the
osseus part of
E. tube opening
Neck of maleus Br of
mandibular div
of trigeminal
nv.
Tenses the
tympanic
membrane
stapedius Conical cavity
and canal
within the
pyramid
Neck of stapes Nv to stapedius
br of facial nv.
Contraction of
stapedius m.
limits stapes
movement thus
preventing
noise trauma to
inner ear
15. Nerves of middle ear
a) Tympanic plexus :- consisting of tympanic br of
glossopharyngeal nv ( Jacobson nv ) and sympathetic
fibres from the caroticotympnic nv. comes from the
sympathetic plexus around the Internal carotid
artery.tympanic plexus supplies the medial surface of
tympanic membrane , tympanic cavity , mastoid air
cells and bony E . Tube.
b) Chorda tympani nv :- it is a br of facial nv. And carries
the gustatory fibres from the anterior 2/3 rd of
tongue and parasympathetic secretomotor fibres to
the submaxillary and sublingual salivary glands.
16. Middle ear mucosa
Mucous membrane of nasopharynx is
continuoua with the midle ear cleft.
Anterior and inferior part Cilliated collumner epithelium
Posterior part Cuboidal type
Attic and nastoid air cells Flat non cilliated epithelium
Eustachian tube Cilliated pseudostratified columner
epithelium
